Methods and systems for producing seamless composite images without requiring overlap of source images

ABSTRACT

A method for producing seamless composite images without requiring overlap of source images is disclosed. A plurality of source images are acquired and combined to produce a seamless composite image. The combining of the plurality of source images to produce a seamless composite image is performed without requiring overlap of image regions of the plurality of source images.

TECHNICAL FIELD

Embodiments of the present invention pertain to methods and systems forproducing seamless composite images without requiring overlap of sourceimages.

BACKGROUND ART

Some conventional image acquisition systems have the capacity to combineindividual images for the purpose of producing composite images thatdetail an enlarged field of view. These image acquisition systems usemethodologies that rely upon the capture of the images by one or morecameras. In order to combine the images that are captured, someconventional systems rely on the overlap of image regions of thecaptured source images.

The quality of a composite image is constrained by the imagery that isused in its creation. It should be appreciated that the resolutioninvolved and the number of viewpoints that are considered are importantfactors that impact the creation of composite images. The greater theresolution and number of viewpoints provided the greater the spatialresolution of the resultant composite image. While digital still camerasare reaching mega-pixel dimensions at nominal cost (e.g., providingincreasingly high resolution images), the spatial resolution provided bydigital video systems lags far behind that offered by digital stillcameras.

Although multi-viewpoint camera systems have been in existence since thedawn of photography, most conventional image analysis is based uponsingle camera views. It should be appreciated, that although stereo andmoving video cameras can provide more viewpoints, the actual utilizationof simultaneous acquisition from a large number of perspectives remainsrare as it relates to such imaging systems. A principal reason for thelow resolution and limited number of viewpoints that are conventionallyemployed in personal computer (PC) imaging systems is the high bandwidthnecessary to support sustained data movement from numerous videosources. The data is provided to a computer memory and, eventually, to adisplay, at the conventional supply rate of 30 frames per second.Moreover, access to high-bandwidth multiple-stream video has beenlimited.

Bandwidth issues arise at the display end of conventional imagingsystems as well. This is because moving large amounts of digital videoseverely taxes current PC architectures. Real-time display of these datarequires a judicious mix across peripheral component interconnect (PCI),PCI-X, and accelerated graphics port (AGP) buses distributed overmultiple display cards.

The creation of composite images (e.g., mosaicking) involves combiningsource images captured from a plurality of camera viewpoints. The sourceimages are derived from viewpoint associated video streams and are usedto form the composite image. A conventional approach to the creation ofcomposite images involves finding points that correspond in thecontributing images and computing stitching homographies that relatetheir perspectives. This approach derives from the situation whereimages are collected from arbitrary positions, such as in hand heldcapture. There, the features for deriving each homography must come fromthe acquired images themselves. If the camera views share a center ofprojection, the features can be chosen from anywhere in the overlappingimages and their homographies will be valid throughout the scene viewed.However, when they don't share a projection center, the features must becollected from a shared observation plane and the homography may onlyproduce seamless composite images for imagery in that plane.

For the reasons outlined above, conventional systems that compositeimages are relegated to low-resolution implementations that employ alimited number of viewpoints. The limited number of viewpoints providesa limited capacity to produce panoramas from acquired images that havehigh spatial resolution. The performance of conventional systems isfurther limited by their reliance on the use of overlapping image datato generate homographies. The requirement that the source images used tocompose a composite image overlap decreases the size of the view anglethat can be imaged as it prevents the imaging of non-overlapping viewsthat can cover a wider measure of space.

DISCLOSURE OF THE INVENTION

A method for producing seamless composite images without requiringoverlap of source images is disclosed. A plurality of source images areacquired and combined to produce a seamless composite image. Thecombining of the plurality of source images to produce a seamlesscomposite image is performed without requiring overlap of image regionsof the plurality of source images.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthis specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention:

FIG. 1A shows a camera system that produces seamless composite imageswithout requiring overlap of the source images that constitute eachcomposite image according to one embodiment of the present invention.

FIG. 1B shows a block diagram of a camera system that produces seamlesscomposite images without requiring overlap of the source images thatconstitute each composite image according to one embodiment of thepresent invention.

FIG. 1C illustrates the imaging of seated conferees participating in avideo conferencing session using a camera system for producing seamlesscomposite images without requiring overlap of acquired images accordingto one embodiment of the present invention.

FIG. 1D is a top perspective view of conferees shown in FIG. 1B andillustrates the positioning of conference participants in the imagingplane of camera system according to one embodiment of the presentinvention.

FIG. 1E illustrates how a common image plane is formed from the planesof focus of a plurality of imagers that are employed by multi-imagercamera system according to one embodiment of the present invention.

FIG. 2 is a top perspective view of conferees shown in a more circularconfuration that that of FIG. 1C and illustrates the positioning ofconference participants in a deeper imaging plane of the camera systemaccording to one embodiment of the present invention.

FIG. 3 shows source images captured by a multi-imager camera system andline features that are used to relate the source images according to oneembodiment of the present invention.

FIG. 4A illustrates the formation of a seamless composite image usingline based homographies according to one embodiment of the presentinvention.

FIG. 4B illustrates the formation of a seamless composite image usingline based homographies according to one embodiment of the presentinvention.

FIG. 4C illustrates the formation of a seamless composite image usingline based homographies according to one embodiment of the presentinvention.

FIG. 4D illustrates the formation of a seamless composite image usingline based homographies according to one embodiment of the presentinvention.

FIG. 5 shows an exemplary dataflow diagram illustrating the flow ofvideo data where six video imagers are employed in a multi-imager camerasystem that employs central processing unit (CPU) processing accordingto one embodiment of the present invention.

FIG. 6 illustrates an application of graphics acceleration according toone embodiment of the present invention.

FIG. 7 shows a flowchart of the steps performed in a method of producingseamless composite images without using overlap of source imagesaccording to one embodiment of the present invention.

FIG. 8 shows a flowchart of the steps performed in a method forcalibrating a plurality of imagers to produce a seamless composite imagewithout using overlap of source images according to one embodiment ofthe present invention.

The drawings referred to in this description should not be understood asbeing drawn to scale except if specifically noted.

BEST MODE FOR CARRYING OUT THE INVENTION

Reference will now be made in detail to various embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction withthese embodiments, it will be understood that they are not intended tolimit the invention to these embodiments. On the contrary, the inventionis intended to cover alternatives, modifications and equivalents, whichmay be included within the spirit and scope of the invention as definedby the appended claims. Furthermore, in the following description of thepresent invention, numerous specific details are set forth in order toprovide a thorough understanding of the present invention. In otherinstances, well-known methods, procedures, components, and circuits havenot been described in detail as not to unnecessarily obscure aspects ofthe present invention.

For purposes of the following discussion the term “composite image” isintended to refer to an image that is formed from two or more acquiredor captured images. Moreover, the term “mosaicking” is intended to referto the process of creating seamless composite images. The term “sourceimage” is intended to refer to images from which a composite image isformed. The term “imager” is intended to refer to a component of acamera system that captures images. The term “homography” is intended torefer to a mathematical object that relates the perspectives of sourceimages. In one embodiment, these homographies are determined byconstraints shared by source images and are utilized to combine thosesource images seamlessly.

System for Producing Seamless Composite Images According to OneEmbodiment of the Present Invention

FIG. 1A shows a camera system 100 that produces seamless compositeimages without requiring overlap of the source images that constituteeach composite image according to one embodiment of the presentinvention. A block diagram 100A of camera system 100 is shown in FIG.1B. In the present embodiment, the composite images are formed bycombining a plurality of source images that are captured using aplurality of imagers according to one embodiment of the presentinvention. In the FIG. 1A embodiment, camera system 100 includes,imagers 101-105 and image compositor 107.

Imagers 101-105 capture respective source images from the respectiveviewpoints of the imagers 101-105. The captured source images arecombined to form seamless composite images (e.g., virtual images, mosaicimages etc.). The composite images are created using source images thatcorrespond to respective image streams that are generated by therespective imagers 101-105. The composite images that are created usingthe captured images can yield a panoramic view that can not be derivedfrom any of the individual views.

While one embodiment of the system may have a common plane arrangedfront to-parallel to the camera views, in which case the individuallenses of the imagers will all be focused at about the same distance. Itshould be appreciated that the focal distances of the lenses of imagers101-105 may be set independently to accommodate an orientation of acommon plane that is not orthogonal to their general view direction.Although camera system 100 is depicted in FIG. 1 as including threeimagers, other arrangements that include other numbers of imagers can beemployed according to exemplary embodiments. In one embodiment imagerscan be employed as a part of a pan tilt zoom (PTZ) imaging system thatprovides frame selection within the composite image.

In exemplary embodiments, the relationship of captured (e.g., acquired)images can be fixed before capture. When the relationship of capturedimages is fixed before capture, dynamic registration can be replaced byonce only analysis. In one embodiment, imagers 101-105 are configuredbeforehand for a desired panorama-shaped image, and the knownrelationship of the imagers 101-105 is used to repeatedly compose theframe in real time at minimal central processing unit (CPU) cost.

Combiner 107 combines the source images that are acquired by imagers101-105 to produce a seamless composite image (e.g., virtual image,mosaic image etc.). In one embodiment, the composite image is created ina manner that does not require overlap of an image region of theacquired image. In one embodiment, this is accomplished by using linefeatures to combine the source images (see discussion made withreference to FIG. 3). The line features enable the combiner 107 toidentify relationships that exist among the source images that can beutilized to combine the source images seamlessly.

In operation, camera system 100 can be situated so that objects that aredesired to be imaged are located within it's imaging plane, e.g., planeof focus POF, shared or common observation plane, etc., (see discussionmade with reference to FIG. 1C). In one embodiment, a plurality ofimagers are configured to capture respective source images fromrespective portions of the shared observation plane. In the presentembodiment, seamless composite images are formed by combining the sourceimages using a resampling mechanism that utilizes homographies based online features.

It should be appreciated that the size of the view angle that can beimaged by camera system 100 is significantly increased as compared toconventional systems because it does not rely on image overlap toproduce composite images. The larger view angle allows the imaging ofpanoramas that cover a wider measure of space. For this reason aplurality of lower resolution imagers can be used to produce panoramasthat have increased spatial resolution for the number of imagers thatare provided. Consequently, greater spatial resolution can be achievedwith less additional bandwidth.

In one embodiment, the line features that are used can be visible in(and in some cases extend across) several images and can providecorrespondences between the images that eliminates the necessity ofhaving significant overlapping of the source images from which acomposite image is formed (see discussions made herein).

In one embodiment, because the presence of overlap can be limited tooperations that ensure the continuity of the composite image, thepresence of overlap can be minimized. Moreover, because a series ofsource images that do not overlap can cover a wider angle than the samenumber of similarly formatted source images that do overlap, the numberof imagers that are necessary to cover space desired to be imaged can bereduced. This feature of exemplary embodiments of the present invention,minimizes the number of imagers that is required to construct a desiredpanoramic view. It should be appreciated that this maximizes both theusefulness of acquired pixels and the efficiency of the image processing(capacity to image a wider angle using fewer imagers).

In one embodiment, the creation of seamless composite images (e.g.,video mosaicking) can be employed to capture panoramic views (e.g., wideangled and unbroken views) of video conferencing participants forpresentation at remote sites. In such embodiments the observations fromseveral multi-viewpoint imagers are combined to simulate the performanceof a much costlier mega-pixel video camera. The result can bereformatted to a desired panoramic view shape.

FIG. 1C illustrates the imaging of seated conferees participating in avideo conferencing session using a camera system 100 for producingseamless composite images without requiring overlap of acquired images.In FIG. 1C camera systems 100 and 110 are placed where seated conferees121, 123 and 125 are located within their imaging planes, e.g., plane offocus (POF), (see reference 127 in FIG. 1D) of camera systems 100 and110 as is illustrated in FIG. 1D. FIG. 1D is a top perspective view ofconferees 121, 123 and 125 shown in FIG. 1C and illustrates an exemplarypositioning of conference participants for imaging in the imaging plane127 of camera system 100. In one embodiment, imaging plane 127 is formedfrom a combination of the image planes of the imagers that are a part ofcamera system 100 and thus represents the common image plane of theimagers that are employed in camera system 100. In one embodiment thefocal distances of the lenses of the imagers are set independently toaccommodate an orientation of the common plane that is not orthogonal totheir general view direction.

FIG. 1E illustrates how a common image plane (e.g., 127) is formed fromthe POFs of a plurality of imagers (e.g., 101, 103 and 105 in FIG. 1A)that are a part of the multi-imager camera system 100. Referring to FIG.1E, the image planes (POF1, POF2 and POF3) of the imagers that areemployed in camera system 100 provide a common image plane 127. Asmentioned above, for imaging purposes, the camera system 100 ispositioned so that conferees are located in common image plane 127.

FIG. 2 shows the conferees situated around a table. Their position mightappear to make the homography invalid, since they do not lie in or neara plane—their separation is indicated as dZ (depth of focus).Nevertheless, this arrangement will be acceptably handled by thehomography. if the centers of projection of the individual imagers ofcamera system 100 are sufficiently near each other.

The Use of Line Features

FIG. 3 shows source images captured by a multi-imager camera system andline features that are used to relate the source images according to oneembodiment of the present invention. FIG. 3 shows source images301A-301C, calibration plane 303 and line features 305A-305D. FIG. 3illustrates the use of line features 305A-305D which are projected intocalibration plane 303 and used to identify relationships between sourceimages 301A-301C. The relationships are used to generate a respectivehomography H1, H2 and H3 for respective source images 301A-301C.

It will be obvious to those skilled in the art that there is a certainnumber of such lines that must be observed and certain relations ofindependence that must be satisfied in order for the homographyestimation process to be valid.

In exemplary embodiments, using line features 305A-305D, high-resolutionwide-angled panorama views can be constructed from a minimum number oflow-resolution imagers (e.g., 101-105 in FIG. 1). In such embodiments,an homography H relating two source images I and I′ (for instance 301Aand 301B) with corresponding points x and x′ and lines I and I′ is givenby the equations:x′=HxI′=H⁻¹I

Referring again to FIG. 3, since in one embodiment lines (e.g., linefeatures 305A-305D) can be employed that are visible in (and in somecases extend across) several source images (e.g., 301A-301C),correspondences among source images 301A-301C can be identified withoutsignificant source image overlap. Since overlap is only needed forcontinuity of the resulting composite image, the need for overlap can beminimized (to zero) and the number of imagers (e.g., 101-105 in FIG. 1)needed to construct a desired panoramic view is reduced. In suchembodiments, the usefulness of acquired pixels is maximized whileprocessing is made more efficient.

It should be appreciated that the size of the view angle that can beimaged by a camera system (e.g., 100 in FIG. 1) employing the abovedescribed line feature image compositing methodology is significantlyincreased as compared to conventional systems because image overlap isnot required in order to produce seamless composite images. The largerview angle allows the imaging of panoramas that cover a wider measure ofspace. For this reason, by employing the herein described methodology, aplurality of lower resolution imagers can be used to produce panoramasthat have increased spatial resolution for the number of imagers thatare provided. Consequently, greater spatial resolution can be achievedwith less additional bandwidth.

It should be appreciated that lines are similar to points in thatcollinear lines are like lines of coincident points, parallel lines arelike lines of collinear points, and a minimum of four observations ingeneral position are needed to form an homography with eight degrees offreedom (in a preferred embodiment, many more can be used in order toimprove precision and stability). However, the extended spatial supportof line based solutions presents an added advantage over point-basedsolutions in that localization of a line is more robust. Morespecifically, when presented with the same number of observations oflines and points, better estimates can be generated using the lines.

Line Based Homographies

FIGS. 4A-4D illustrate the formation of a seamless composite image usingline based homographies according to one embodiment of the presentinvention. FIG. 4B shows source images 401, 403 and 405 that contributeto the desired seamless composite image (e.g., mosaic) shown in FIG. 4Dand the line features 411 (shown in FIG. 4A as line features 411A-411C)that relate the perspectives of source images 401, 403 and 405 fromwhich homographies of source images 401, 403 and 405 are computed. FIG.4C shows a view of the composite image without blending (unblendedregions 407 and 409 are shown in FIG. 4B).

In one embodiment, homographies can be generated by: (1) projecting linefeatures that are detectable by an imager array (see discussion madewith reference to FIG. 3), (2) correcting the line features for lensdistortion, (3) estimating line features using a least squares fitter,and (4) passing the line features to a homography solver. The homographyfrom one imager (e.g., 101-105 in FIG. 1) to another can be derived asthe transpose inverse of the solution determined by treating thehomogeneous representation of each line as if it were a point andsolving for the point-wise homography (see equation above).

It should be appreciated that in one embodiment lens correction andluminance and color adjustments are made to bring images into agreementon color and, brightness, and to correct for lens distortions. In suchembodiments the geometric correction is part of the re-sampling, and thecolor and brightness corrections make the content photometrically morecorrect.

Alternately, the line based homography can be determined directly fromthe linear estimates. In one embodiment, having the homographies thatrelate one imager to another, allow the homographies to be chainedtogether to determine the transforms that bring any involved imager intoa global frame of reference. Initially, the global frame may be chosenas one of the imager frames (for instance the center imager).Subsequently, a derived global frame may be constructed that encompassesthem all.

In one embodiment, a re-sampling mechanism (e.g., lookup table etc.)that contains pre-computed values that are used to compose a compositeimage from its contributing components is constructed after an outputsize within the dataset corresponding to a constructed frame isdetermined. The table can carry bilinear interpolation indices andweights that are used to compose each destination pixel. These indicesmap pixels that make up the resultant composite image through eachimager homography and reposition the mapped point to account for anyobserved lens-induced curvatures. In one embodiment, the vast majorityof pixels can be seen by only one imager. In cases where several imagerssee a pixel, the contributions of the pixels can be blended. In oneembodiment, the metric employed is linear interpolation (regions ofoverlap are determined, and the pixel weights of the contributing pixelsseen by respective imagers are computed by distance from that sourceimage's boundary).

CPU and GPU Based of Production of Seamless Composite Images Accordingto One Embodiment

CPU Based Production of Seamless Composite Images

FIG. 5 shows an exemplary dataflow diagram illustrating the flow ofvideo data where six video imagers are employed in a multi-imager camerasystem that employs CPU processing according to one embodiment of thepresent invention. FIG. 5 illustrates a beneficial bandwidth andcomputation distribution scheme where parallelized CPU processing isemployed. In the FIG. 5 embodiment, synchronized imagers 501A-501Fgenerate parallel streams of video data that are delivered to RAMstorage units 505 via a bus 503 (e.g., PCI etc.). Subsequently, thedigital video 507 receives parallelized color conversion 508 andcompositing and blending (if necessary) 509 and is delivered to adisplay 511 that includes RAM storage units 511A and graphics board511B.

In moving large amounts of digital video 507 current PC architecturesare severely taxed. Real-time display of these data requires a judiciousmix across peripheral component interconnect (PCI), PCI-X, andaccelerated graphics port (AGP) buses distributed over multiple displaycards, which present significant bandwidth challenges. In oneembodiment, with these bandwidth issues in mind, a distributedparallelized processing scheme such as is illustrated in FIG. 5 can beemployed that is enabled both by the multi-imager system performanceexhibited by exemplary embodiments of the present invention and by theadvanced graphics processing units (GPUs) that are available for modernPCs (see discussion below).

In one embodiment, the compositing of images can be performed by a PCprocessor that uses a re-sampling mechanism (e.g., lookup-table etc). Asdiscussed above, computation can be parallelized to exploit multipleprocessors. In this embodiment, re-mapping can be designed to scalebased on numbers of camera pixels and size of display.

GPU Based Production of Seamless Composite Images

FIG. 6 illustrates an application of graphics acceleration according toone embodiment of the present invention. FIG. 6 shows blocks thatrepresent the video streams 601, that are generated by synchronizedimagers, a data bus 603, color conversion operations 605,compositing/blending operations 607 and AGP graphics hardware 609. FIG.6 illustrates an embodiment where compositing and blending operations605 (e.g., mosaicking operations) are performed by the AGP graphicshardware 609 and preceded by CPU color conversion operations 605.

In the FIG. 6 embodiment, the use of graphics processing can beexploited for use in panorama building. In this embodiment, for displayoriented tasks, re-sampling vectors can be treated as static imagegeometry and the streaming video can be treated as dynamic textures. Insuch embodiments, the static image geometry can be downloaded (reshapingthe source images), allowing compositing and blending operations to beperformed by the AGP graphics hardware 609 (e.g., GPU hardware). Thesubsequent video is streamed to the display.

In the FIG. 6 embodiment, GPU “mosaicking” can be performed considerablyfaster than CPU “mosaicking.” In such embodiments, the CPU's task can besolely one of color converting the camera video from one format toanother, and then passing the imagery to the graphics card. In anotherembodiment the processor load can be reduced even further by performingcolor re-sampling in the GPU rather than converting video into RGBbefore sending it to the graphics board. In this embodiment, busbandwidth load can also be reduced which is an important considerationwhen cameras and displays share resources with other activities.

Another advantage of the GPU approach to “mosaicking” is that the costof producing the composite image is independent of its size. Bycontrast, high costs are incurred for large images when CPU-basedcompositing is employed. In one embodiment, if the video stream is sentto a handheld device or ramped up for a very large display surface, thedifferent scalings can be handled transparently in the graphics card.

In one embodiment, the graphics processing units (GPUs) of a PC can beused for the re-sampling to provide better scaling. In this embodiment,a beneficial computational use of available graphics processing is made.It should be appreciated that the use of graphics processing can beuseful in display oriented applications.

FIG. 7 shows a flowchart of the steps performed in a method of producingseamless composite images without using overlap of source imagesaccording to one embodiment of the present invention.

At step 701, a plurality of source images are acquired (e.g., captured,imaged etc.).

At step 703, the plurality of source images are combined to produce aseamless composite image. In one embodiment, the combining of theplurality of source images to produce a seamless composite image isperformed without requiring overlap of image regions of the plurality ofsource images.

It should be appreciated that by employing the methodology describedwith reference to FIG. 7 the size of the view angle that can be imagedis significantly increased as compared to conventional systems becausethe methodology of FIG. 7 does not rely on image overlap to producecomposite images. The larger view angle allows the imaging of panoramasthat cover a wider measure of space. For this reason a plurality oflower resolution imagers can be used to produce panoramas that haveincreased spatial resolution for the number of imagers that areemployed. Consequently, greater spatial resolution can be achieved withless additional bandwidth.

FIG. 8 shows a flowchart of the steps performed in a method forcalibrating a plurality of imagers to produce a seamless composite imagewithout requiring overlap of source images according to one embodimentof the present invention.

At step 801, line features are identified that are observed in (andperhaps extend across) each imager frame of said plurality of imagers.

At step 803, homographies are calculated using the line features thatrelate each imager frame of the plurality of imagers to at least oneother imager frame of the plurality of imagers.

At step 805, a lookup table is constructed that is used to map pixelsthat constitute the composite image through the correction of lensdistortions and the use of homographies.

In exemplary embodiments data can be composited, for example, in bothVGA and extended graphics array (XGA) format into linear mosaics in realtime. In one embodiment, at distances of about ten feet from cameras toconference participants, satisfactory planar homographies can becomputed. In an alternate embodiment, satisfactory planar homographiescan be computed at other distances. In one embodiment, blending makes“ghosting” that can appear from distant objects that lie away from thecalibration plane, nearly unnoticeable. In a realized embodiment, imagesare produced by three-imager “mosaicking” were judged comparable withthose from a broadcast-quality digital video camera that costssignificantly more.

Embodiments of the present invention may exploit a multi-viewpointimaging architecture. The combination of high-bandwidth acquisition withdistributed peripheral computation provided by exemplary embodiments ofthe present invention enable video streaming and shaping free ofexpensive optics and electronics, and significant PC processing. In oneembodiment, other elements of multi-viewpoint processing such as lenscorrection toward the camera heads (in one embodiment, a modular cameradesign can include an option of processing at the head) can be employedas a means of increasing performance scalability. In addition furtheradvances in GPU distributed processing can serve to support themulti-viewpoint display of the present embodiment.

1. A method for producing seamless composite images without requiringoverlap of source images, comprising: acquiring a plurality of sourceimages; combining said plurality of source images to produce a seamlesscomposite image, wherein said combining said plurality of source imagesto produce a seamless composite image is performed using said pluralityof source images without requiring overlap of image regions of saidplurality of source images; and utilizing a re-sampling mechanism to mappixels that constitute said composite images through a lens distortioncorrection and a homography for each of said plurality of imagers afteran output size within a dataset corresponding to a constructed frame isdetermined.
 2. The method of claim 1 wherein said combining saidplurality of source images is performed using line features determinedfrom said source images.
 3. The method of claim 1 wherein said combiningis performed on images that have a relationship that is determinedbefore the capture of said images.
 4. The method of claim 2 wherein saiduse of line features is through determination of a homography thatrelates one imager in a plurality of imagers to another.
 5. The methodof claim 4 wherein a series of homographies is used to place all of saidimagers in a reference plane that is common to all of said imagers. 6.The method of claim 2 wherein said line features are lines that arevisible in at least two said source images and wherein objects fromwhich said source images are derived are positioned within a commonplane.
 7. The method of claim 1 wherein at least a portion of saidcombining is performed using a graphics processing unit (GPU).
 8. Themethod of claim 6 wherein the focal distances of the lenses of saidplurality of imagers are set independently to accommodate an orientationof the common plane that is not orthogonal to their general viewdirection.
 9. The method of claim 1 wherein said plurality of imagersare apart of a pan tilt zoom (PTZ) imaging system that provides frameselection within said composite image.
 10. A system for producingseamless composite images without requiring overlap of source images,comprising: a plurality of imagers for acquiring a plurality of saidsource images; and a combiner for combining said plurality of saidsource images to produce a seamless composite image, wherein saidcombining said plurality of said source images to produce a seamlesscomposite image is performed using said plurality of source imageswithout requiring overlap of image regions of said plurality of saidsource images; and a re-sampling mechanism for mapping pixels thatconstitute said composite image through a lens distortion correction anda homography of each imager after an output size within a datasetcorresponding to a constructed frame is determined.
 11. The system ofclaim 10 wherein said combiner combines said plurality of said sourceimages using line features determined from the images.
 12. The system ofclaim 10 wherein said combiner combines said source images based on arelationship that is determined before a capture of said source images.13. The system of claim 11 wherein each of said plurality of imagers arerelated to at least one other imager by using said line features todetermine a homography.
 14. The system of claim 10 wherein all of saidimagers are placed in a reference plane that is common to all saidimagers using a series of homographies.
 15. The system of claim 13wherein said line features are lines which are visible in at least twosource images and wherein said source images are derived from objectsthat are located within a common plane.
 16. The system of claim 15wherein focal distances of lenses of said plurality of imagers are setindependently to accommodate an orientation of said common plane that isnot orthogonal to their general view direction.
 17. The system of claim10 wherein at least a portion of said combining is performed using agraphics processing unit (GPU).
 18. The system of claim 10 wherein saidsystem is contained in an imager housing.
 19. The system of claim 10wherein said plurality of imagers are a part of a pan tilt zoom (PTZ)imaging system that provides frame selection within said compositeimage.
 20. A method for calibrating a plurality of imagers to produce aseamless composite image without requiring overlap of source images,comprising: identifying line features that are visible in each imagerframe of said plurality of imagers; and making computations using saidline features that relate each imager frame of said plurality of imagersto at least one other imager frame of said plurality of imagers; andconstructing a re-sampling mechanism for mapping pixels that constitutesaid composite image through said computations after an output sizewithin a dataset corresponding to a constructed frame is determined. 21.The method of claim 20 wherein said computations constitutehomographies.
 22. The method of claim 21 wherein a series of saidhomographies is used to place each imager of said plurality of imagersinto a common reference plane.
 23. The method of claim 20 whereinobjects from which said source images are derived are positioned withina common plane.
 24. The method of claim 20 wherein said plurality ofimagers are a part of a pan tilt zoom (PTZ) imaging system that providesframe selection within said composite image.